Ultracentrifuge with rotor speed identification

ABSTRACT

Provisions are made for electronically identifying the maximum allowable speed of an ultracentrifuge rotor for the purpose of supplying the identification information to a rotor overspeed control to prevent spinning a rotor beyond its designed top speed. The top surface of the rotor carries a number of annular bands which may be either black or white. The color of the annular band in each band position is detected by means of an electronic circuit including a light source, a photocell detector, and a transistor switch for each band. Each transistor switch conducts when the annular band from which it receives reflected light is black, but does not conduct when the annular band is white. Each conducting switch puts out a steady voltage signal of different amplitude. The voltage output signals of the transistor switches are added to generate an analog control signal identifying the rotor by the color combination of its annular bands. If there are three annular band positions on the rotor, each being either black or white, there are eight possible values of the analog control signal representing eight different maximum allowable rotor speeds.

United States Patent 11 1 Camilliere 1 51 July 17,1973

1 1 ULTRACENTRIFUGE WITH ROTOR SPEED [73] Assignee: Electro-Nucleonics,Inc., Essex County, NJ.

[22] Filed: Dec. 23, 1970 [21] Appl. No.: 100,850

1521 US. Cl. 233 1 B, 318/313 51 1111.01 801d 21/26 58 Field of Search233/1 R, 23 R, 24,

233/19 R, l B; 318/340, 313; 307/117; 192/84 P, 103 R PrimaryExaminer.lordan Franklin Assistant Examiner-George H. KrizmanichAttorney-Henry T. Burke, P. E. Henninger, Lester W. Clark, Gerald W.Griffin, Thomas P. Moran, Howard J. Churchill, R. Bradlee Boal,Christopher C. Dunham and Robert Scobey [57] ABSTRACT Provisions aremade for electronically identifying the maximum allowable speed of anultracentrifuge rotor for the purpose of supplying the identificationinformation to a rotor overspeed control to prevent spinning a rotorbeyond its designed top speed. The top surface of the rotor carries anumber of annular bands which may be either black or white. The color ofthe annular band in each band position is detected by means of anelectronic circuit including a light source, a photocell detector, and atransistor switch for each band. Each transistor switch conducts whenthe annular band from which it receives reflected light is black, butdoes not conduct when the annular band is white. Each conducting switchputs out a steady voltage signal of different amplitude. The voltageoutput signals of the transistor switches are added to generate ananalog control signal identifying the rotor by the color combination ofits annular bands. If there are three annular band positions on therotor, each being either black or white, there are eight possible valuesof the analog control signal representing eight different maximumallowable rotor speeds.

8 Claims, 6 Drawing Figures Patented July 17, 1973 3 Sheets-Sheet 1 ZZZINVENTOR. JOHN CAM/L L/ERE ATTORNEY Patented July 17, 1973 I5Sheets-Sheet 5 mokom 1 N VE N TOR. Joy/v CAM/1. LIE/Q5 ULTRACENTRIFUGEWITH ROTOR SPEED IDENTIFICATION BACKGROUND OF THE INVENTION Theinvention is in the field of ultracentrifuge apparatus and particularlyrelates to controlling rotor speeds. In many ultracentrifuge uses themaximum speed of the rotor must be precisely and accurately controlled.In a given ultracentrifuge different rotors may be used interchangeably,with each rotor characterized by a different maximum allowable speed. Ameans for detecting, without human intervention, which rotor is in theultracentrifuge and for automatically setting a conventional rotoroverspeed control to the maximum allowable rotor speed is thereforedesirable. It is desirable to identify the maximum allowable rotor speedwhether the rotor is spinning or stationary.

One prior art method of identifying the maximum allowable speed of arotor utilizes a disk affixed to the rotor and painted with alternateblack and white stripes emanating radially from the rotor center ofrotation. A photosensor is mounted above the disk to detect the ratio ofblack to white and to convert the ratio information into an analogcontrol signal for setting an overspeed control. In this analog systemthe rotor must be spinning to get a proper reading; the reading from astationary rotor is not meaningful. Variations in light intensity orphotocell sensitivity can cause errors in the reading.

Another prior art method for identifying the maximum allowable speed ofa particular rotor involves the use of a mechanical arm which contactsthe rotor and detects its diameter, with the diameter readingrepresenting an indication of the allowable top rotor speed. This methodutilizes a system which is primarily mechanical and is thereforedifficult to maintain and is limited in range.

SUMMARY OF THE INVENTION The ultracentrifuge rotor speed identificationsystem of this invention provides for accurate and unambiguousidentification of both stationary and spinning rotors by decoding aplurality of annular bands arranged concentrically with the rotor axisof rotation and affixed to the rotor, each band being characterized by areflection index of either a first or a second distinct value, togetherwith an electronic circuit for detecting the type of band in each bandposition and for providing, on the basis of the detected information, acontrol signal for overspeed control. The circuit includes a lightsource for illuminating each of the annular bands and a photocelldetector for each band, each photocell detector being exposed to lightreflected from its annular band. The circuit further includes processingmeans connected to the photocell detectors for generating an overspeedcontrol signal in the form of a voltage signal whose amplitude varies asa function of the combination of photocell detectors exposed to lightreflected for annular bands having reflection index of one of the firstand second values.

For example, if the annular bands are either black or white, and thereare three band positions in the form of concentric rings about the axisof rotation of the rotor, there are eight possible combinations to bedetected by the photocells because there are three variables of binaryvalue. Given the same combination of bands the photocell detectors putout the same combination of signals whether the rotor is spinning orstationary. Reasonable variations in light intensity of the light sourceor of the sensitivity of the photocell detectors do not cause errors inreading because the output of the photocells is not analog but digital.The digital signal represented by the photocell detector resistivitiesis converted to an analog signal for controlling the overspeed controlby means of a circuit including a transistor switch for each photocelldetector which is responsive to the resistivity state of the detector,and a decoding circuit for decoding the outputs of the transistorswitches.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representationof the upper portion of an ultracentrifuge having a replaceable rotor, astationary housing and a detector for detecting the top allowable speedof the rotor.

FIG. 2 is a sectional view along line 22 of FIG. 1.

FIG. 3 is a sectional view along line 3-3 of FIG. 1.

FIG. 4 is a sectional view along line 44 of FIG. 3.

FIG. 5 is a perspective detailed view of three annular bands afflxed tothe rotor and of a supporting structure for the detector.

FIG. 6 is a schematic diagram of a circuit for converting the digitallycoded output of a plurality of photocell detectors into an analogcontrol signal.

DETAILED DESCRIPTION A typical ultracentrifuge includes a stationaryhous ing generally indicated at 10, a replaceable rotor generallyindicated at 12, driving means to spin the rotor, and an overspeedcontrol means for preventing rotor spinning above a preselected angularspeed. The rotor driving means and the overspeed control areconventional elements and are indicated as labelled blocks 14 and 16respectively in FIG. 6. Different rotors 12 may be inserted into thehousing 10, and each different rotor 12 may have a different maximumallowable rota tional speed. The overspeed control 16 must therefore beset to suit the particular rotor 12 which is to be spun by the rotordriving means 14.

For the purpose of identifying its maximum allowable speed, each rotor12 is provided with a plurality of annular bands 18a, 18b and 180 whichare positioned concentrically about the axis of rotation of the rotor 12which is perpendicular to the plane of FIG. 2 and passing through thecenter of the rotor 12. Although three bands are shown in the examplediscussed herein, it should be understood that any other suitable numberof bands may be used depending on the number of different maximumallowable rotational speeds which are to be identified. Each of theannular bands 18a, 18b, and 18c has a light reflection index of either afirst or a second value. In a particular example, each of the hands maybe either black or white. If the top surface of the rotor 12 isoriginally colored black, then only white bands 18 need to painted orotherwise afflxed to the top surface 120.

The bands 18a, 18b and 18c may be of either one of two colors which havedifferent indexes of reflection, or they may be of either one of twotextures which have different reflection indexes. The fact that thereare two possible indexes of reflection for each band gives the band abinary value. Thus, two bands can represent up to four combinations ofindexes of reflection, three bands can represent up to eightcombinations of indexes of reflection, etc.

The presence of an annular band of a particular index of reflection in aparticluar band position is detected by a means including a box-shapedblock 20 supported above the top surface 12a of the rotor 12 by means oftwo L-shaped brackets 22 and 24 affixed to opposing sides of the block20 by means of bolts 22a and 24a threaded into the block 20. The upperportions of the brackets 22 and 24 are affixed to a top lid a of theultracentrifuge housing 10 by means of bolts 22b and 24b threaded intothe lid 10a. The block is thus affixed to the stationary housing 10 ofthe ultracentrifuge and is held stationarily above the top surface 120of the rotor 12. The rotor 12 may be removed in conventional manner bydropping it out of the housing 10, and it may be replaced bya new rotor12 which may have different combinations of reflective indexes of itsbands 18a, 18b, and 18c.

The block 20 is provided with a plurality of light source bores 26a, 26band 260 which are in planes transverse to the radius of the rotor 12 andare oriented to point toward a radius of the top surface 12a of therotor 12. Each of the light source bores 26a, 26b and 26c and contains alight 28 enclosed in a sleeve 30 retained against a narrowed lowerportion of the bore by means of a spring. In reference to FIG-3 showingthe bore 26c, the sleeve 30 enclosing the light 28 is retained againstthe narrowed lower portion 26d of the bore 260 and is urged downwardlyby means of a spring 32. The spring is retained by retaining a plate 34affixed to the top surface 20a of the block 20 by bolts 36 threaded intothe block 20. The edge of the plate 34 facing the bores 26a, 26b and 26chas comb-like cutouts 36a, 36b and 36c such that the top ends of thelight source bores 26a, 26b and 26c are only partially covered by theplate 34 and wires 38 can run to the lights 28 for the purpose ofsupplying the lights with power.

For each of the light source bores 26a, 26b and 260 there is acorresponding photocell detector bore. Each of the photocell detectorbores is in the same planetransverse to a radius of the rotor 12 as itscorresponding light source bore. Referring to FIG. 3, a photocelldetector bore 40c corresponds to the light source bore 260 and is in thesame plane transverse to a radius of the rotor 12. The photocelldetector bore 400 is shaped similarly to the light source bore 260 andhas a narrowed lower portion 40d which retains a photocell detector 42urged against the narrowed portion 40d by a spring 44. The edge of theretaining plate 34 on the side of the photocell detector bore 400 isshaped similarly to the edge toward the light source bore 260 and hassimilar cutouts 36a. The retaining plate 34 holds the spring 44 andallows the exit from the bore 400 of wires 46 which are connected to atransistor switch described later in this specification.

Referring specifically to FIGS. 3 and 5, it is seen that each pair of alight and a photocell detector are oriented in their respective boressuch that they cooperate with a paticular one of the annular bands 18a,18b and 18c. The light source bore 26c is oriented such that a beam oflight 480 emanating from the light 28 in the light source bore 26c isdirected to the annular band 180 and is reflected therefrom as reflectedbeam 50c. The orientations of the light source bore 260 and of thephotocell detector bore 40c and the distance between the bores and thetop surface 120 of the rotor 12 are such that the reflected beam 500enters the photocell detector bore 400 and impinges on the photocelldetector 42 retained therein. Similarly a light beam 48b originating atlight source 26b is reflected from the annular band 18b and enters thephotocell detector bore 40b as reflected beam 50b. A light beam 48a isgenerated in the light source bore 26a and, after reflection from theannular band 18a, enters the photocell detector bore 40a as reflectedbeam 50a.

It is evident that the intensity of the reflected beam 500 depends onthe index of reflection of the annular band the intensity of thereflected beam 50!) depends on the index of reflection of the annularband 18b; and the intensity of the reflected beam 50a depends on theindex of reflection of the annular band 180. If the index of reflectionof each of the annular bands is either of a first value or of a secondvalue, then the intensity of each reflected beam is either of a firstvalue or of-a second value. The intensity of each of the reflected beams50a, 50b and 500 is thus a binary parameter and the intensity values ofthree beams can represent up to eight different combinations.

The intensity of each of the reflected beams 50a, 50b and 50c isdetected by the circuit shown in FIG. 6 which includes transducerswitches 52a, 52b and 520, one associated with each of the transistorswitches 52a, 52b and 520, which include one of the photocell detectors42a, 42b and 420 and serves to generate a zero voltage output signalwhen the photocell is illuminated by a reflected beam of high intensity,and a different voltage signal when the reflected beam is of lowintensity. Thus, the transistor switch 52c includes the photocelldetector 420 which is illuminated by the beam 50c reflected from theannular band 180. When the index of reflection of the annular band 18cis low and the in tensity of the reflected beam 50c is correspondinglylow, the resistance of the photocell detector 420 is high. When theresistance of the photocell detector 42:: is high, a PNP transistor 560is biased by means of a biasing resistor 58c and a negative voltagesource 54 such that it in turn biases an NPN transistor 60a to conductcurrent from a negative voltage source 62 across a weighting resistor64a. The transistor switch 52b operates in a similar manner, with thebase of a PNP transistor 56b connected to a voltage dividing networkcomprising a biasing resistor 58b and the photocell detector 42bconnected between the negative voltage source 54 and ground, and withthe base of an NPN transistor 60b connected to the collector of the PNPtransistor 56b. When the light beam reflected from the annular band 18illuminating the photocell detector 42b has low intensity, theresistance of the photocell detector 42b is high and the NPN transistor60b is biased to conduct current from the negative voltage source 62across a weighting resistor 64b. Similarly when the beam 50a reflectedfrom the annular band [8a illuminating the photocell detector 42a haslow intensity, then the resistance of the photocell detector 42a is highand an NPN transistor 60a is biased by means ofa PNP transistor 56a toconduct current from the negative voltage source 62 across a weightingresistor 64a.

When the beam 500 reflected from the annular band 18c is of highintensity, then the resistance of the photocell detector 42c drops andthe NPN transistor 600' stops conducting. Similarly when the resistanceof the photocell detector 42 drops, the NPN transistor 60b stopsconducting; and when the resistance of the photocell detector 420 drops,the NPN transistor 60a stops conducting.

The weighting resistors 64a, 64b, and 641: are connected as the inputresistance to a conventional integrated decoding circuit 66. Theweighting resistors 64a, 64b and 64c and the integrated circuit 66 arechosen such that the NPN transistor 600 (when conducting) contributes0.5 volts to the output of the circuit 66; the NPN transistor 66b (whenconducting) contributes 1.0 volts to the output of the circuit 66; andthe NPN transistor 600 (when conducting) contributes 2.0 volts to theoutput of the circuit 66. This choice results in eight possible voltagelevels at the output of the integrated circuit 66 differing from eachother in steps of 0.5 volts. The possible combinations of conducting andnonconducting states of the transistors 60a, 60b and 600 and the voltageat the outputs of the integrated circuit 66 resulting from eachcombination are listed in the chart below in which the conducting stateof the NPN transistors is designated by on and the nonconducting statesare designated by off:

NPN NPN NPN Output transistor transistor transistor of integrated 60c60b 60a circuit 66 in volts off off off 0 ofi' off on 0.5 off on off 1.0off on on 1.5 on off ofi 2.0 on off on 2.5 on on off 3.0 on on on 3.5

In the table directly above the off state of a transistor corresponds tohigh reflection index of the annular band with which it is assciated andthe on state of a transistor corresponds to a low reflection index ofthe annular band with which it is associated. For example, assume thateach of the annular bands 18a, 18b and 18c is either black or white.Then if only the annular band 18a is white while annular bands 18b and18c are black,

only the transistor 60a of the transistor switch 52a is conducting andthe voltage at the output of the integrated circuit 66 is 0.5 volts; ifthe annular bands 18a and 18b are white while the annular band 18c isblack, then the output of the circuit 66 is 1.5 volts, etc.

The output of the integrated circuit 66 is connected to a conventionaloverspeed control 16 which prevents the rotor driving means 14 fromspinning the rotor 12 at speeds above the maximum allowable speed forthe rotor defined by the voltage level of the signal at the output ofthe circuit 66. For example, the overspeed control 16 may be set toprevent spinning the rotor 12 above 30,000 rpm when the voltagesignalfrom the circuit 66 is 0.5 volts, to prevent spinning the rotorabove 35,000 rpm when the voltage signal from the circuit 66 is 1 volt,etc.

In the embodiment described above, three annular bands are used todefine one of eight possible rotor speeds. It should be clear, however,that the number of annular bands depends only on the number of possiblerotor speeds that need be defined. Thus, two bands can be used if onlyup to four different speeds are to be defined, four bands can be used ifup to [6 rotor speeds is to be defined, etc. The annular band should beof one of two possible indexes of reflection, and the provision of twopossible reflection indexes can be achieved in any one of a number ofpossible manners. For example,

the bands may be either black or white, or the top surface 12a of therotor 12 may be of generally black background with only white bands, ifany, affixed onto it, or an extra disk may be affixed to the top surface12a of the rotor 12, with the disk having annular bands of either afirst or a second index of reflection.

It is noted that in the embodiment described above, the rotor 12 is' notcontacted by the stationary portion of the means for determining itsmaximum allowable speed. It is also noted that the determination isindependent of whether the rotor 12 is moving or stationary, because theindex of reflection of each band is uniform around the circumference ofthe band and the reflected beam of light has the same intensityregardless of which portion of a particular band reflects it.

In recapitulation, the invention relates to an ultracentrifuge apparatusincluding a stationary housing generally indicated at 10, a replaceablerotor 12, driving means 14 to spin the rotor and an overspeed control 16for preventing the rotor spinning means from imparting to the rotorspeeds above a preselected limit. The improvement is in means forgenerating information indicative of the maximum allowable spin speed ofthe rotor 12 and for conveying the information to the overspeed controll6, and comprises a plurality of annular bands such as bands 18a, 18band 18c arranged concentrically with the axis of rotation of the rotor12 and affixed to the-top surface 12 of the rotor, with each of thebands 18a, 18b and characterized by a reflection index of either a firstor a second value. As one example, the two distinct reflection indexvalues may be defined by coloring the annular bands either black orwhite. A supporting means in the form of a block 20 supports a lightsource in the form of lights 28 and a plurality of photocell detectorssuch as detectors 42a, 42b and 420. The block 20 has a plurality oflight source bores 26a, 26b and 260 and a plurality of photocelldetector bores 40a, 40b and 40c oriented in respect to and spaced fromthe rotor such that for each band there is a light 28 illuminating theband by a beam of light which beam is reflected and impinges as areflected beam upon a photocell detector. A processing means comprisinga plurality of transistor switches such as switches 52a, 52b and 520 isconnected to the photocell detectors to generate a voltage signal whoseamplitude varies as a function of the combination of photocell detectorsexposed to light reflected from annular bands having reflection index ofone of a first orsecond value. I

I claim:

l. Ultracentn'fuge apparatus including: a stationary housing, areplaceable rotor, driving means to spin the rotor, and an overspeedcontrol means for preventing rotor spinning above a preselected angularspeed; wherein the improvement is in means for generating informationindicative of the maximum allowable spin speed of the rotor and forconveying said information to the overspeed control means, comprising: i

a. a plurality of annular bands arranged concentrically with the rotoraxis of rotation and affixed to the rotor, each band characterized by areflection index of either a first or a second value, said values beingdistinct from each other;

b. a light source for illuminating each of the annular bands;

c. a plurality of photocell detectors, one photocell detector for eachof the annular bands;

(1. means for supporting the light source spaced from the rotor, and forsupporting the photocell detectors spaced from the rotor, with eachphotocell detectors esposed to light reflected primarily by its annularband, the resistance of each photocell detector varying as the functionof the amount of light reflected by its band; and processing meansconnected to said photocell detectors for generating a voltage signalwhose amplitude varies as a function of the combinations of photocelldetectors exposed to light reflected from annular bands havingreflection index of one of said first and second values.

2. Apparatus as in claim 1 wherein annular bands characterized by areflection index of the first value are white are and annular bandscharacterized by a reflection index of the second value are black withthe photocell detectors exposed to light reflected from white bandshaving lower resistance then that of photocell detectors exposed tolight reflected from black bands.

3. Apparatus as in claim 2 wherein the annular bands form a part of therotor surface and the rotor surface is black, except for white annularbands thereon.

4. Apparatus as in claim 1 wherein the supporting means comprises ablock affixed to the ultracentrifuge housing and having a lower surfacefacing the annular bands on the rotor and having a plurality of lightsource bores each enclosing a light spaced inwardly from the lowersurface of the block, each light source bore being oriented to directlight to a different annular band, said block also including a pluralityof detector bores, each detector enclosing a photocell detector spacedinwardly from the lower surface of the block and being oriented toexpose the enclosed detector to light reflected from a different annularband.

5. Apparatus as in claim 4 wherein the rotor has a relatively flat topsurface and the annular bands form a part of the rotor top surface, thetop rotor surface being black except for white bands, each of theannular bands being either black or white, with black bands beingindistinct from the rotor top surface.

6. Apparatus as in claim 1 wherein the processing means comrpises aplurality of transistor switches, one transistor switch for eachphotocell detector, each switch comprising a circuit including aphotocell detector and biased to conduct when the photocell detector hasresistance defined by illumination by light reflected from a band havingrflection index of said first value, and biased not to conduct when thephotocells resistance is defined by illumination by light reflected froma band having reflection index of said second value.

7. Apparatus as in claim 6 wherein the output of each conductingtransistor switch is a steady voltage signal of a different preselectedamplitude, and wherein means is provided for adding the voltage signaloutputs of conducting transistor switches to generate an overspeedcontrol signal, the amplitude of the common control signal being the sumof the steady voltage outputs signals of the conducting transistorswitches.

8. Apparatus as in claim 7 including a first, a second and a thirdtransistor switch, with the differences between the amplitudes of thefirst and the second, and between the second and the third transistorswitches being the same.

1. Ultracentrifuge apparatus including: a stationary housing, areplaceable rotor, driving means to spin the rotor, and an overspeedcontrol means for preventing rotor spinning above a preselected angularspeed; wherein the improvement is in means for generating informationindicative of the maximum allowable spin speed of the rotor and forconveying said information to the overspeed control means, comprising:a. a plurality of annular bands arranged concentrically with the rotoraxis of rotation and affixed to the rotor, each band characterized by areflection index of either a first or a second value, said values beingdistinct from each other; b. a light source for illuminating each of theannular bands; c. a plurality of photocell detectors, one photocelldetector for each of the annular bands; d. means for supporting thelight source spaced from the rotor, and for supporting the photocelldetectors spaced from the rotor, with each photocell detectors esposedto light reflected primarily by its annular band, the resistance of eachphotocell detector varying as the function of the amount of lightreflected by its band; and e. processing means connected to saidphotocell Detectors for generating a voltage signal whose amplitudevaries as a function of the combinations of photocell detectors exposedto light reflected from annular bands having reflection index of one ofsaid first and second values.
 2. Apparatus as in claim 1 wherein annularbands characterized by a reflection index of the first value are whiteare and annular bands characterized by a reflection index of the secondvalue are black , with the photocell detectors exposed to lightreflected from white bands having lower resistance then that ofphotocell detectors exposed to light reflected from black bands. 3.Apparatus as in claim 2 wherein the annular bands form a part of therotor surface and the rotor surface is black, except for white annularbands thereon.
 4. Apparatus as in claim 1 wherein the supporting meanscomprises a block affixed to the ultracentrifuge housing and having alower surface facing the annular bands on the rotor and having aplurality of light source bores each enclosing a light spaced inwardlyfrom the lower surface of the block, each light source bore beingoriented to direct light to a different annular band, said block alsoincluding a plurality of detector bores, each detector enclosing aphotocell detector spaced inwardly from the lower surface of the blockand being oriented to expose the enclosed detector to light reflectedfrom a different annular band.
 5. Apparatus as in claim 4 wherein therotor has a relatively flat top surface and the annular bands form apart of the rotor top surface, the top rotor surface being black exceptfor white bands, each of the annular bands being either black or white,with black bands being indistinct from the rotor top surface. 6.Apparatus as in claim 1 wherein the processing means comrpises aplurality of transistor switches, one transistor switch for eachphotocell detector, each switch comprising a circuit including aphotocell detector and biased to conduct when the photocell detector hasresistance defined by illumination by light reflected from a band havingrflection index of said first value, and biased not to conduct when thephotocell''s resistance is defined by illumination by light reflectedfrom a band having reflection index of said second value.
 7. Apparatusas in claim 6 wherein the output of each conducting transistor switch isa steady voltage signal of a different preselected amplitude, andwherein means is provided for adding the voltage signal outputs ofconducting transistor switches to generate an overspeed control signal,the amplitude of the common control signal being the sum of the steadyvoltage outputs signals of the conducting transistor switches. 8.Apparatus as in claim 7 including a first, a second and a thirdtransistor switch, with the differences between the amplitudes of thefirst and the second, and between the second and the third transistorswitches being the same.